Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-10-01
2002-04-09
Shalwala, Bipin (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S063000, C315S169400
Reexamination Certificate
active
06369781
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface-discharge type AC plasma display panel (hereinafter, referred to as “AC-PDP”), and more particularly to a method of driving the AC-PDP and a driving circuit therefor.
2. Description of the Background Art
A variety of studies has been made in a field of PDP (Plasma Display Panel) used as a slim television or display monitor. One of AC-PDPs having a memory function is a surface-discharge type AC-PDP, and structure and driving method of the PDP will be discussed below with reference to
FIGS. 32 and 33A
to
33
E.
FIG. 32
is a perspective view showing a structure of a surface-discharge type AC-PDP in the prior art, and the surface-discharge type AC-PDP having this structure is disclosed in Japanese Patent Application Laid Open Gazettes 7-140922 and 7-287548. In
FIG. 32
, a surface-discharge type AC-PDP
101
C comprises a front glass substrate
102
C serving as a display surface and a rear glass substrate
103
C opposed to the front glass substrate
102
C with a discharge space therebetween. On a surface of the front glass substrate
102
C on the side of the discharge space, n first electrodes
104
C and n second electrodes
105
C are extendedly provided in pairs. As shown in
FIG. 32
, when the first and second electrodes
104
C and
105
C have metal assistant electrodes (bus electrodes) on part of their surfaces, respective electrodes including the metal assistant electrodes may be termed “a first electrode
104
C” and “a second electrode
105
C”. Further, the first and second electrodes
104
C and
105
C are also termed row electrodes
104
C and
105
C, respectively. In the AC-PDP
101
C, a dielectric layer
106
C is so provided as to cover the row electrodes
104
C and
105
C. In some cases, as shown in
FIG. 32
, an MgO film
107
C made of MgO (magnesium oxide) which is a dielectric is formed by evaporation on a surface of the dielectric layer
106
C. In this case, the dielectric layer
106
C and the MgO film
107
C are termed “dielectric layer
106
AC” as a unit.
On a surface of the rear glass substrate
103
C on the side of the discharge space, m third electrodes
108
C (hereinafter, referred to as “column electrode
108
C”) are so provided extendedly as to cross the row electrodes
104
C and
105
C. Between adjacent column electrodes
108
C, a barrier
110
C is extendedly provided in parallel to the column electrodes
108
C. The barrier
110
C separates discharge cells and works as a pole for supporting the PDP lest the PDP should be broken by atmospheric pressure. On a surface of the column electrode
108
C and a side-wall surface of the barrier
110
C, phosphor layers
109
C for emitting red, green and blue lights are provided orderly in stripes.
The front glass substrate
102
C and the rear glass substrate
103
C having the above structure are sealed to each other, and in a space between these glass substrates
102
C and
103
C, a discharge gas such as an Ne—Xe mixed gas and He—Xe mixed gas is enclosed by a pressure not more than atmospheric pressure. In the surface-discharge type AC-PDP
101
C having this structure, the discharge space comparted by the row electrodes
104
C and
105
C in a pair and the column electrodes
108
C is a discharge cell for the PDP
101
C, i.e., a pixel.
Next, a principle of a display operation of the above prior-art PDP will be discussed.
First, a voltage pulse is applied to the row electrodes
104
C and
105
C to cause a discharge. An ultraviolet ray generated by this discharge excites the phosphor layer
109
C, to cause the discharge cell to emit. In this discharge, electrons and ions generated in the discharge space move to the row electrodes
104
C and
105
C of reverse polarity and are stacked on a surface of the dielectric layer
106
AC on the row electrodes
104
C and
105
C. The electrons and ions stacked on the surface of the dielectric layer
106
AC are termed “wall charges”. The amount of wall charges depend on an externally-applied voltage value and therefore a potential of the wall charges can not exceed the externally-applied voltage value.
An electric field induced by the wall charges works to weaken an applied electric field and therefore the discharge rapidly disappears as the wall charges are generated. After the discharge disappears, when a voltage pulse of reverse polarity is applied between the row electrodes
104
C and
105
C, a discharge occurs again since an electric field in which the applied electric field and the electric field induced by the wall charges are superposed is substantially applied in the discharge space. Thus, once a discharge occurs, successive discharge can be caused by applying an applied voltage (hereinafter, referred to as “sustain voltage”) lower than the voltage at the time when the discharge starts. Therefore, applying the sustain voltage (hereinafter, referred to also as “sustain pulse”) between the row electrodes
104
C and
105
C with its polarity reversed alternately makes it possible to stationarily sustain the discharge. Hereinafter, the discharge is referred to as “sustain discharge”.
The sustain discharge can be kept as far as the sustain pulse is applied until the wall charges disappear. Extinguishing the wall charges is referred to as “erase” and generating the wall charges on the dielectric layers
106
AC (MgO film
107
C) in the initial stage of the discharge is referred to as “write”. With respect to any cell in a screen of the AC-PDP, write is first performed, and thereafter the sustain discharge is performed, to display characters, figures and images. Performing quick operation of the write, sustain discharge and erase allows display of motion pictures.
According to the above principle of operation, in the discharge on the rise of the applied pulse, the effective voltage consists mainly of the externally-applied voltage and supplementally of the wall charges. Therefore, this discharge is termed “discharge mainly induced by externally-applied voltage”.
On the other hand, if the externally-applied voltage is very high, in some times, the wall charges produce a potential not less than the firing voltage. In this case, on the fall of the applied pulse, the discharge can occur only by the wall charges. The discharge with no voltage externally applied is referred to as “self-erase discharge”. Since the effective voltage of the discharge is given mainly by the wall charges, the discharge is referred to as “discharge mainly induced by wall charges”. Since the externally-applied voltage may be supplementally applied in a direction to increase the discharge in the discharge mainly induced by wall charges, the definition of “discharge mainly induced by wall charges” herein includes the discharge with the supply of the external voltage.
When the AC-PDP is driven by using both the “discharge mainly induced by externally-applied voltage” and the “discharge mainly induced by wall charges”, since the wall charges are reduced after termination of the discharge mainly induced by wall charges, in order to subsequently cause the discharge main induced by externally-applied voltage, it is necessary to (i) apply higher externally-applied voltage or (ii) apply the externally-applied voltage in a state where the firing voltage is lowered by the space charges generated in the discharge mainly induced by wall charges. Especially, the case (ii), i.e., the driving method using the pulse memory effect can lower a current density per one discharge, and can thereby improve a discharge efficiency and reduce a peak current value. Further, the discharge mainly induced by wall charges ends with a certain amount of wall charges according to the discharge characteristics of the cell even if a voltage variation exists in the panel. Hence, when the discharge mainly induced by externally-applied voltage is subsequently caused, it is possible to uniform the light-emitting intensity. Therefore, by the driving method of (ii), it is possible to prevent variation in luminance of the panel surface.
Next, a prior-art method of
Hashimoto Takashi
Iwata Akihiko
Mitsubishi Denki & Kabushiki Kaisha
Osorio Ricardo
Shalwala Bipin
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